Effect of foliar spray with potassium and calcium on the physiological response and relative value of stability of lettuce plant under drought stress conditions

Abstract

This research was carried out in Erah Research Station/ Sewida Agricultural Research Center/ General Commission for Scientific Agricultural Research/ Syria in 2021. The aim of this research was studying the effect of combined foliar spraying with potassium (K) and calcium (Ca) on  physiological characteristics and relative value of stability of lettuce plants under drought conditions. The cultivation was achieved under three different levels of irrigation (60-80-100% of the field capacity), and three concentrations of combined foliar spraying with potassium (0-1-2 mg/l) and calcium (0-0.5-1mg/l) compounds were applied. The results showed that the gradual increase in drought level led to a gradual decrease in most physiological indicators(relative water content and content of carbohydrate and proline), and a gradual increase in water deficit and chlorophyll content in leaves. In addition, the treatment of foliar spray with potassium and calcium led to improve all indicators compared to the untreated plants under drought levels. Also the result of interaction between drought level and spraying did not show any differences in the irrigation level 100% for relative water content and water deficit, while in the irrigation level 80% and 60%, the treatment k(2 g/l)+ ca (0.5 g/l) led to significant increase in relative water content (86.71%) and (86.61%) and the content of proline (439.8 µM /g) and (464.4 µM /g) respectively compared to the control. In the irrigation level 80% and 60% all of treatments was significant compared to the control for the content of carbohydrate and proline. While in the irrigation 60%, the treatment k(2 g/l)+ ca (0.5 g/l) was significant for chlorophyll a (1.09 µg /mg) and b (0.31 µg /mg) and total chlorophyll (1.41 µg /mg) compared to the control. So, foliar application with potassium and calcium had a significant effect on physiological indicators for lettuce plants under drought stress.